There are many applications for which precise control over the amount or rate at which a fluid is dispensed by a pumping apparatus is necessary. In semiconductor manufacturing processes, for example, it is important to control the amount and rate at which photochemicals, such as photoresist chemicals, are applied to a semiconductor wafer.
Many photochemicals used in the semiconductor industry are very expensive, costing a thousand or more per a liter. Additionally, these chemicals may be susceptible to breaking down or gelling within a short time. Therefore, it is advantageous to utilize pumping systems which minimize unused volume and prevent stagnation of fluid contained therein.
Pumping systems, such as those used in semiconductor manufacturing, may utilize a number of diaphragm valves to move or exert pressure on the process fluid. Hydraulic fluid is typically used to assert pressure on one side of the diaphragm to cause the diaphragm to move, thereby displacing the process fluid. The hydraulic fluid could be put under pressure by a pneumatic piston or a stepper motor driven piston.
Existing diaphragm valves are usually round or circular in shape. To get the displacement volume required by dispense pumps, a typical diaphragm valve has to have a diaphragm with a relatively large surface area that is much larger than the area between the inlet and outlet. Consequently, the valve chamber often has a larger than necessary volume and a cross-sectional profile of a circle with a relatively large diameter. This can result in a holdup volume of processing fluid being left in the valve chamber after a dispense operation which, in turn, may cause stagnation of fluid and/or gelling issues. Furthermore, the relatively large diameter of the valve chamber can make controlling pressure drop across the diaphragm valve very difficult which, in turn, may negatively affect precision in pumping operations. In view of at least these issues, there is room for innovations and improvements.